Process for shrinkproofing animal fibers



July 9, 1968 J THORSEN 3,391,986

PROCESS FOR SHRINKPROOFING ANIMAL FIBERS Filed April 6, 1967 SOURCE OF 2 OHLORINE GAS 19 MOISTURIZER AIR 1 I4 1 X 3 I5 Y TOWIND-UP 7 REEL l TREATED FIBROUS MATERIAL DRIER T POWER SOURCE ROLL OF FIBROUS MATERIAL TO BE TREATED WALTER J. THORSE N INVE NTOR BY KW TTORNEY 3,391,986 IPRQCESS FOR SHRINKIPROUFHNG ANIMAL FIBERS Walter J. Thorsen, El Cerrito, Caiiti, assignor to the United States of America as represented by the Secretary of Agriculture Filed Apr. 6, 1967, Ser. No. 62,9,87ti l Claims. (Cl. 8-128) ABSTRACT OF THE DISCLQSURE Fibrous material of animal origine.g., wool or mohairis exposed to a corona discharge zone into which is fed a mixture of air and chlorine gas, typically, a mixture of about 14 volumes of air and one volume of chlorine. By this contact of the fibers with ozone and other gases formed in the corona cell, the shrinkage properties of the fibers are greatly improved.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the poWer to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to and has among its objects the provisions of novel processes for shrinkproofing proteinous animal fibers, e.g., wool, mohair, and the like. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.

The single figure in annexed drawing illustrates apparatus for carrying out a preferred modification of the process of the invention.

In my copending application Ser. No. 442,561, filed Mar. 24, 1965, I have disclosed that wool and other animal fibers may be shrinkproofed by placing the fibers in a locus where ozone is generated. Typically, this is done by providing a high-voltage electrical discharge zone at normal atmospheric pressure and open to atmospheric air, and placing the fibers in said zone for a short period of time. While in the zone, the fibers are contacted with ozone and other gaseous substances produced by the electrical discharge, and as a result the shrinkage properties of the fibers are substantially improved. It is further explained in the aforesaid application that the procedure has many advantages, for example, only a brief processing time of about 2 to seconds is needed; continuous operation is feasible because of the short processing time; and the apparatus for applying the process is simple and inexpensive-there is no need for separate ozone-generating and fiber-treating devices as required in prior systems involving treatment of fibers with preformed ozone.

In accordance with the present invention the procedure of the aforesaid application is employed with the modification that chlorine, as well as air, is introduced into the electrical discharge zone. I have found that the addition of chlorine gas results in a surprising increase in the shrink-resistance of the roduct. For example, two runs on wool conducted under otherwise identical conditions but wherein air alone was used in one, and air plus chlorine (14 vols. to one vol.) in the other, provided the following results: The product of the first run (air alone) had a shrinkage of 22 minutes, whereas the product of the second (air-l-chlorine) had a shrinkage time of 92 minutes. (Shrinkage was measured by the ball shrinkage test described in detail in the examples below.)

In a typical practice of the invention the electrical discharge system is provided with a gas inlet arrangement,

1 nied States Patent 0 and a stream of air and chlorine is fed into the system via this inlet. For optimum results, the stream should contain about 14 volumes of air per volume of chlorine. However, it has been observed that improved results-as compared with air alone-are obtained with proportions ranging from about 5 to about 50 volumes of air per volume of chlorine.

The process of the invention not only provides the advantage of attaining a high degree of shrinkproofing but also retains the various advantages of the prior process of Ser. No. 442,561 to wit:

A primary advantage is that the desired result is attained very rapidly, for example, in a matter of l to 20 seconds in contrast to the processing time of at least 1 minute and preferably about 3 minutes required with known processes, for example, that disclosed in my Patent 3,149,906 wherein an ozone generator is provided and the gas issuing from this generator, together with admixed steam, is blown against the fibrous material for a period of 1 to 10 minutes to achieve the desired result.

Since the process of the invention requires but a very brief processing time, it is especially adapted for application on a continuous basis as in treating long lengths of fibrous materials. Because of the short treatment time such continuous processing will not interfere with the orderly flow of the fibrous material through the various steps required to convert the original raw fibers into finished textiles.

The invention involves more efiicient use of ozone, i.e., less ozone is required per unit weight of fibrous material treated. Since the fibers are located in the zone where the ozone is formed, the ozone can immediately contact the fibers and there is little opportunity for loss of ozone. This is in sharp contrast to systems wherein a gas stream containing ozone is blown through a textile material; in such case much of the ozone will fail to contact the fibers and be lost.

The apparatus used for applying the process of the invention is simple and inexpensive. Although some gashandling equipment is needed, it is not at all complicated, and, of course, there is no need for providing apparatus for creating high pressure or vacuum, i.e., the system of the invention is operated at essentially normal (atmospheric) pressure.

The dyeing properties of the fibers are essentially unaltered by the process of the invention. This means that the products can be dyed following conventional formulations and schedules. Accordingly, the process of the invention can be applied to a conventional textile processing line without interference with the dyeing procedures normally employed in the plant.

Another advantage of the process of the invention is that the intrinsic properties of the fibers such as their acid solubility, alkali solubility, tensile strength, and abrasion resistance are not impaired.

A further item is that no pressureresistant (nor vacuum-resistant) equipment is required; the entire procedure is carried out at normal atmospheric pressure.

Another point is that wool yarns treated in accordance with the invention have an enhanced tensile strength as compared to the untreated yarns.

I have also observed that especially good results are obtained when the fibrous material is at least partially dried before introducing it into the discharge zone, and when the gas stream fed into the said zone contains moisture. In a practice of this modification of the invention, the fibrous material to be treated is subjected to a conventional drying operation so that its moisture content is less than about 5%, prior to feeding it into the electrical discharge zone. As to the gas stream fed into the discharge zone: Ordinary atmospheric air contains sufiicient moisture to attain the desired effect. However, it is generally preferred to saturate the air with moisture for best results. This can be done in conventional manner, for example, by passing the air stream through water or through a chamber filled with crushed rock, Berl saddles, beads, or the like, and sprayed with water. Although optimum results are attained when the fibrous material is dried before treatment and the incoming gas is humidified, the invention may be practiced without incorporation of these features, thus to still achieve the improved rcsults yielded by the basic procedure heretofore described.

One form of apparatus for applying the process of the invention is illustrated in the annexed drawing. This modification of apparatus is adapted for continuous treatment of long lengths of fibrous material, and includes the optional features of providing means for drying the fibrous material before treatment and humidifying the incoming gas stream. The construction and operation of the apparatus are explained below.

The discharge device, or corona cell, generally designated as 1 includes plates 2 and 3 of dielectric material such as glass, separated by a small distanceabout 4 to 10 mm. In contact with the respective plates 2 and 3 are electrodes 4 and 5, made of aluminum, copper, or other electrically-conductive metal. The electrodes are provided with tubes 6 and 7 for circulation of a heat exchange medium therethrough whereby the discharge device may be cooled (or heated) to maintain it at a desired temperature level.

For energizing corona cell 1 there is provided a step-up transformer 8. The secondary winding 9 of the transformer is connected to electrodes 4 and 5. (Symbols x, x designate an electrical connection omitted from the figure to avoid confusion with the other parts.) The primary winding 10 is connected to an AC power source. The center tap 11 of the secondary winding is preferably grounded, as shown. The parameters of the energizing system and the power source are chosen to provide an EMF across electrodes 4 and of about 10,000 to 25,000 volts at a frequency of about 60-5000 c.p.s. Generally, better results are attained at the higher frequencies in this range. Energized as above set forth, a corona discharge takes place in the space between plates 2 and 3. Thus, the space emits a diffuse violet-colored glow which appears as a series of brush discharges.

A stream of gas-air, chlorine, and water vapor (either adventitious or deliberately added)is supplied by pipe 18 to the space between plates 2 and 3. The corona discharge acts upon these gaseous materials within the said space. As a result, in addition to the introduced substances-oxygen, nitrogen, chlorine, and water vapor in their normal statesthere is present the following:

Monatomic oxygen (0). Monatomic chlorine (Cl).

Monatomic oxygen in both negatively and positively charged states. Monatomic chlorine in both negatively and positively charged states.

Molecular oxygen (0 vibrationally excited by the visible light.

Molecular oxygen in both negatively and positively charged states.

Ozone (0 Chlorine dioxide (C Ozone, vibrationally excited by the ultraviolet light.

Ozone in both negatively and positively charged states.

Oxides of nitrogen, including nitrogen pentaxide, nitrogen dioxide, and nitrous oxide.

Hydrogen peroxide. Hydroxy free-radicals (OH-).

From the above, it is apparent that various reactive forms of oxygen, nitrogen, and chlorine are present in the discharge area. Many of the highly reactive speciesfor example, the vibrationally excited and charged speciesdecay rapidly and cannot be removed from the discharge area in a gas stream. Accordingly, direct exposure of fibrous material to the discharge area in accordance with the invention produces reactions and fiber modifications which are different from those obtained when the gaseous products of the discharge area are removed therefrom and only then applied to a fibrous material.

In operation, corona cell 1 is energized and the textile material from roll 13 is continuously drawn through the system by the sets of driven rollers 14 and 15. The material first passes through drier 16 wherein its moisture content is reduced to below 5%. Then, the material passes through the cell 1, and the treated material 17 may then be wound up on a reel and further processed as desired. The speed of rollers 14 and 15 is so adjusted that the fibrous material remains in the discharge area for a period long enough to attain the desired shrinkproofing effect but not long enough to damage the fibers. This time will generally range from about 2 to 20 seconds. Also during operation, the heat-exchange fluid (for example, a conventional silicone oil) is circulated through tubes 6 and 7 to maintain cell 1 at a temperature of about to 145 C., preferably about 100 C. Ordinarily, in operation of the system the heat-exchange fluid serves to keep the temperature at the desired level by dissipating heat, i.e., heat produced by the corona cell in forming the gaseous substances in the discharge area and heat produced as these substances react with the fibrous material being treated. On the other hand, when the system is started up, it is cold and the fluid is operated in a heating cycle to warm the cell to the desired temperature level.

For introducing gases into corona cell 1, there is provided a conduit 18 made of polytetrafluoroethylene or other insulating, chlorine-resistant material. Pump 19, which may be of the metering type, receives atmospheric air from the open end 18a of the conduit and propels it through moisturizer 20' into cell 1. At the same time, chlorine gas from source 21 is bled into conduit 18 via feed tube 22. The appropriate ratio of air to chlorine is attained by adjustment of valve 23 in correlation with the feed rate of pump 19. Generally, the chlorine-air mixture is fed into the cell at such a rate that there is an excess over that amount actually needed for reaction with the fibrous material; the excess obviously flows out of the discharge zone since this is open on all sides. Only a small amount of pressure is involved in the operation of pump 19, i.e., that required to overcome the resistance to flow of the gases; the pressure in the discharge zone is atmospheric. Moisturizer 20 may take the form, for example, of a chamber provided with sprays of water to humidity the air passing therethrough.

The process of the invention is applicable to animal fibrous materials such as wool, mohair, cashmere, alpaca, vicuna, camel hair, cattle hair, and other proteinous fibers derived from animal sources. The materials may be in any of various physical forms, e.g., slivers, roving, yarns, top, felts, woven or knitted textiles, etc. Usually, it is preferred to treat the fibrous material before it has been fabricated into a textile. Especially preferred is the treatment of thin webs of fibersfor example, card webbingfollowing which the treated material is formed into yarns and then into textile products. Since the process of the invention does not impair the desirable properties of the fibers, materials treated in accordance with the invention may be employed in all the conventional applications of fibrous materials as in production of garments of all kinds.

The invention is further demonstrated by the following illustrative examples:

Example 1 In these runs the corona cell 1 was as shown in the drawing. Dielectric plate 2 was of borosilicate (Pyrex) glass, /s" thick, 10" wide, and 10 long. Dielectric plate 3 was of Micamat-mica flakes bonded with a silicone glass, 0.015" thick, 10 wide, and 10" long. The gap between the plates was A". The corona cell was energized with a current at 18,200 volts, 415 c.p.s., and was maintained at 98 C.

The flow of chlorine gas into the corona cell was maintained constant at 0.00484 cubic feet per minute at standard conditions (hereinafter designated as s.c.f.m.). The flow of air (taken from the atmosphere and necessarily containing some moisture but with no additional moisturizing) was varied during the experiment, as designated below.

Each run involved treatment of wood in its undried condition. Each sample of wool was 1 gram in weight, spread out into a thin web about 100 sq. inches in area. Time of each run was 5 seconds. In a control run, no chlorine was added; air alone was introduced into the corona cell.

The treated wool samples and a sample of the untreated wool were tested for shrink resistance by the loose-fiber feltability (or shrinkage) test. In this test one gram of the material is put in a 120-ml. vessel with 50 ml. of pH 1.0 HCl-KCl buffer and then the vessel is stoppered and placed on a Desaga shaker, whereby the vessels are shaken at a rate of 175 shakes per minute. The shaking is continued until the material forms a ball 25 mm. in diameter. The time required to attain this effect indicates the shrinkage character of the fibers. Thus, a longer time indicates that the fibers felt and shrink to a lesser extent. In other words, a longer time for the fibers to form a ball indicates an improvement in resistance to shrinkage.

The results obtained are as follows:

Air Ratio of air Time for wool Run flow, to chlorine, to form 25 mm. s.c.f.rn. voL/vol. ball, min.

0. 072 22 0. 024 5/1 50 0. 048 /1 70 0. 067 14/1 92 0. 088 16/1 84 0. 11 23/1 65 6 0.15 31/1 45 Blank (untreated wool) 16 1 Air alone.

Example 2 These runs were carried out as described in Example 1, with the following exceptions: The air/ chlorine ratio was held at 14/1. The wool before treatment was dried so that its moisture content was less than 5%. The current of gas (air and chlorine) was humidified or dehumidified to various levels as set forth below. The results obtained are as follows:

Humidity of air-chlorine gas stream. Expressed in These runs were carried out as in Example 1 with the following exceptions: The gas stream supplied to the corona cell was varied to provide mixtures of chlorine and (1) air, (2) nitrogen, and (3) oxygen. In a fourth run, air only was used. In all cases, the chlorine flow rate was 0.022 s.c.f.'m. Flow rates of the other gases were approximately seven times that of chlorine. The results are tabulated below:

Time to form Run Gas mixture, ratio by vol. 25 mm. ball,

minutes 1 Air and chlorine, 7/1 70 Nitrogen and chlorine, 7/1 37 Oxygen and chlorine, 7/1 37 4 Air only 18 Blank (untreated wool) 14 An unusual property of fibers treated in accordance with the invention is that their resistance to shrinkage may be canceled and subsequently restored by application of certain procedures described below. The importance of this property is explained as follows: In the preparation of textiles from wool or other animal fibers (both woven and knit goods) it is customary to apply a fulling treatment-the fabric is mechanically worked in a warm aqueous bath containing any of various agents such as alkaline agents or acids, soap, etc. As the name implies, the treatment makes the fabric fuller. Usually, the fabric as it comes from the loom or knitting machine has a threadbare appearance. During the fulling operation the fabric shrinks to a controlled extent so that gaps between adjacent yarns are reduced and the fabric becomes denser and develops a desirable body, texture, and appearance. It is obvious, of course, that if a fiber is shrinkproof, a fabric made therefrom cannot be properly fulled. However, the products of the invention can be temporarily deprived of their shrinkproof quality by application of a cationic surface-active agent such as quaternary ammonium salts containing long-chain alkyl groups, methylol derivatives of long-chain fatty acids, and amides of fatty acids containing more than 8 carbon atoms. When so treated, the fibrous material may be fulled in an aqueous bath at pH below 7 to obtain a desired fulling effect. The fulling operation is most conveniently conducted in an aqueous bath containing a cationic detergent plus acid (hydrochloric or sulphuric, for example) to make the bath acidic. After the fulling operation is completed, the shrink-proof quality of the fibrous material is restored by removal of residual cationic detergent. This can be accomplished in various ways, for example, by extracting the fibrous material with an organic solvent such as 1,1,l-trichloroethane, or with acetone-water solutions saturated with salt, or by washing it with an aqueous medium containing a conventional anionic or non-ionic detergent.

It may further be noted that although restoration of feltability may be accomplished as above described, it is not likely that this effect will take place unintentionally during normal usage of the treated fibrou material. This is the case because restoration of feltability requires both application of a cationic detergent plus acidic conditions whereas in normal usagefor example, in washing alkaline conditions are universally applied, and, under these conditions, the shrink resistance of the treated fibers is retained.

This aspect of the invention is demonstrated by the following illustrative example:

Example 4 W001 yarns which had been exposed to the corona cell as previously described were woven into a fabric. The fabric was cut into several samples, each being treated as follows:

Sample #1Tcsted for shrinkage by the accelerotor method. In this test the sample is milled at 1780 r.p.m. for 2 minutes at 40 C. in an accelerotor with 1% soap (sodium oleate), using a liquor-to-wool ratio of 50 to 1. After this washing operation the sample is dried in air and measured to determine its area, and the shrinkage calculated from the original area of the piece. The accelerotor is described in the American Dyestuff Reporter, vol. 45, p. 685, Sept. 10, 1956.

Sample #2The sample was soaked for 15 minutes in an aqueous solution containing 1% of a long-chain alkyl quaternary amine surface-active agent (stearyl dimethyl benzyl ammonium chloride), held at above 60 C. After this treatment the wool was subjected to a fulling treatment. This was conducted in the accelerotor as explained above except that in this instance the liquor used was water acidified to pH 1 with hydrochloric acid. The shrinkage was measured as an index of the emcacy of the fulling operation.

Sample #3-A sample of wool which had been treated 7 to deprive it of its shrinkproof quality (as described in connection with sample #2) was washed with an aqueous solution containing .05 of a conventional non-ionic detergent, nonylpheuoxy poly(ethyleneoxy)ethanol, and 0.2% of tetrasodium pyrophosphate to restore its shrinkproof quality. It was then washed in the accelerotor as described above.

Control: A sample of fabric prepared from untreated wool was subjected to the shrinkage test described in connection with sample #1.

The results obtained are tabulated below:

Treatment A=exposure to corona cell; Treatment B=applieatlon of quaternary ammonium salt; Treatment C=removal of quaternary ammonium salt by washing with non-ionic detergent.

Having thus described the invention, what is claimed is:

l. A method for treating proteinous animal fibers to increase their shrink resistance which comprises exposing the fibers to a corona discharge zone into which is fed a mixture of air and chlorine.

2. The method of claim 1 wherein the mixture contains air and chlorine in a ratio of about 14 to 1, by volume.

3. The method of claim 1 wherein the corona discharge zone is at essentially atmospheric pressure.

4. The method of claim 1 wherein the fibers are dried prior to exposure to the corona discharge zone.

5. The method of claim 1 wherein the mixture of air 8 and chlorine gas is humidified before feeding to the corona discharge zone.

6. The method of claim 1 wherein the corona discharge zone is maintained at about to C.

7. The method of claim 1 wherein the fibers are wool.

8. The method of claim 1 wherein the time of exposure is about 1 to 20 seconds.

9. The method of claim 1 wherein the corona discharge zone is open to the atmosphere.

10. The method of claim 1 wherein the treated fibrous material is impregnated with an acidified aqueous solution of a cationic surface-active agent to permit fulling, the sotreated material is fulled in an acidified aqueous medium, and shrink resistance is restored to the fulled material by removal of the cationic surface-active agent.

References Cited UNITED STATES PATENTS 396,325 1/ 1889 Brin et al. 1,628,484 5/ 1927 Wilkinson.

1,825,178 9/ 1931 Coghill. 3,149,906 9/ 1964 Thorsen 8--12 FOREIGN PATENTS 6,677 6/ 1915 Great Britain. 247,73 8 2/ 1926 Great Britain. 727,771 4/ 1955 Great Britain. 907,882 10/1962 Great Britain. 575,660 4/ 1924 France.

NORMAN G. TORCHIN, Primary Examiner.

I. C. CANNON, Assistant Examiner. 

